Lollipop charts in Matplotlib - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a basic lollipop chart with matplotlib.

Matplotlib

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [10, 15, 7, 12, 9]

plt.stem(x, y, linefmt='grey', markerfmt='o', basefmt=' ')
plt.xlabel('X axis')
plt.ylabel('Y axis')
plt.title('Basic Lollipop Chart')
plt.[1]()

Drag options to blanks, or click blank then click option'

Abar

Bplot

Cscatter

Dshow

Attempts:

3 left

💡 Hint

Common Mistakes

Using plt.plot() instead of plt.show() to display the plot.

Forgetting to call any function to display the chart.

The plt.show() function displays the plot window with the lollipop chart.

2fill in blank

medium

Complete the code to set the color of the markers in the lollipop chart to red.

Matplotlib

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [10, 15, 7, 12, 9]

plt.stem(x, y, linefmt='grey', markerfmt='[1]', basefmt=' ')
plt.show()

Drag options to blanks, or click blank then click option'

A'ro'

B'ko'

C'go'

D'bo'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'bo' which sets blue markers instead of red.

Forgetting to include the marker style 'o' in the string.

The markerfmt='ro' sets the marker color to red with circle markers.

3fill in blank

hard

Fix the error in the code to correctly plot a lollipop chart with custom line and marker colors.

Matplotlib

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [10, 15, 7, 12, 9]

plt.stem(x, y, linefmt=[1], markerfmt='ro', basefmt=' ')
plt.show()

Drag options to blanks, or click blank then click option'

A'grey--'

B'grey-'

C'grey'

D'grey:'

Attempts:

3 left

💡 Hint

Common Mistakes

Using only 'grey' without a line style causes an error.

Using dashed or dotted line styles when a solid line is expected.

The linefmt parameter requires a format string including color and line style, e.g., 'grey-'.

4fill in blank

hard

Fill both blanks to create a lollipop chart with green stems and blue circle markers.

Matplotlib

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [10, 15, 7, 12, 9]

plt.stem(x, y, linefmt=[1], markerfmt=[2], basefmt=' ')
plt.show()

Drag options to blanks, or click blank then click option'

A'g-'

B'ro'

C'bo'

D'k-'

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up colors or line styles in the format strings.

Using 'ro' for markers when blue markers are requested.

linefmt='g-' sets green solid lines; markerfmt='bo' sets blue circle markers.

5fill in blank

hard

Fill all three blanks to create a lollipop chart with x labels, y values, and a title.

Matplotlib

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [10, 15, 7, 12, 9]

plt.stem([1], [2], linefmt='grey-', markerfmt='ro', basefmt=' ')
plt.[3]('Lollipop Chart Example')
plt.show()

Drag options to blanks, or click blank then click option'

Ax

By

Ctitle

Dxlabel

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping x and y data in the stem function.

Using plt.xlabel() instead of plt.title() for the chart title.

The stem plot uses x and y data; plt.title() sets the chart title.

Practice

1. What is the main purpose of a lollipop chart in data visualization?

easy

A. To compare values using lines and dots for clear differences

B. To show the distribution of data using bars

C. To display data points on a map

D. To create 3D surface plots

Solution

1. Step 1: Understand lollipop chart basics

   A lollipop chart uses lines and dots to compare values clearly, making differences easy to see.

2. Step 2: Compare with other chart types

   Bar charts show distribution, maps show locations, and 3D plots show surfaces, which are different from lollipop charts.

3. Final Answer:

   To compare values using lines and dots for clear differences -> Option A

4. Quick Check:

   Lollipop chart = lines + dots comparison [OK]

Hint: Remember: lollipop = line + dot comparison [OK]

Common Mistakes:

• Confusing lollipop charts with bar charts
• Thinking lollipop charts show geographic data
• Assuming lollipop charts are 3D plots

2. Which matplotlib function is used to create a basic lollipop chart?

easy

A. plt.bar()

B. plt.scatter()

C. plt.plot()

D. plt.stem()

Solution

1. Step 1: Identify the function for lollipop charts

   Matplotlib's plt.stem() creates lollipop charts by drawing lines with markers at the ends.

2. Step 2: Differentiate from other plotting functions

   plt.bar() makes bar charts, plt.scatter() makes scatter plots, and plt.plot() makes line plots, not lollipop charts.

3. Final Answer:

   plt.stem() -> Option D

4. Quick Check:

   Use plt.stem() for lollipop charts [OK]

Hint: Use plt.stem() to combine lines and dots [OK]

Common Mistakes:

• Using plt.bar() instead of plt.stem()
• Confusing scatter plots with lollipop charts
• Trying plt.plot() which lacks markers by default

3. What will the following code output?

import matplotlib.pyplot as plt
x = [1, 2, 3]
y = [4, 2, 5]
plt.stem(x, y)
plt.show()

medium

A. A bar chart with bars at x=1,2,3 and heights 4,2,5

B. A lollipop chart with stems at x=1,2,3 and heights 4,2,5

C. A scatter plot with points at (1,4), (2,2), (3,5)

D. An error because plt.stem() needs more arguments

Solution

1. Step 1: Understand plt.stem() behavior

   The function plt.stem(x, y) draws vertical lines (stems) from zero to each y value at positions x, with dots at the top.

2. Step 2: Analyze the given data points

   Here, x = [1,2,3] and y = [4,2,5], so stems appear at x=1 with height 4, x=2 with height 2, and x=3 with height 5.

3. Final Answer:

   A lollipop chart with stems at x=1,2,3 and heights 4,2,5 -> Option B

4. Quick Check:

   plt.stem(x,y) = lollipop chart [OK]

Hint: plt.stem(x,y) draws stems at x with heights y [OK]

Common Mistakes:

• Thinking plt.stem() creates bar charts
• Confusing scatter plot with lollipop chart
• Assuming plt.stem() requires extra arguments

4. Identify the error in this code for creating a lollipop chart:

import matplotlib.pyplot as plt
x = [1, 2, 3]
y = [4, 5]
plt.stem(x, y)
plt.show()

medium

A. plt.stem() is not imported correctly

B. plt.show() is missing parentheses

C. x and y have different lengths causing a ValueError

D. No error, code runs fine

Solution

1. Step 1: Check lengths of x and y

   x has 3 elements, y has 2 elements. They must be the same length for plotting.

2. Step 2: Understand matplotlib error

   Matplotlib raises a ValueError when x and y lengths differ because it cannot pair points correctly.

3. Final Answer:

   x and y have different lengths causing a ValueError -> Option C

4. Quick Check:

   Equal length x,y needed [OK]

Hint: Check x and y lengths match before plotting [OK]

Common Mistakes:

• Ignoring length mismatch between x and y
• Thinking plt.show() needs no parentheses
• Assuming plt.stem() import causes error

5. Which code snippet correctly changes the marker color to red?

import matplotlib.pyplot as plt
x = [1, 2, 3, 4]
y = [5, 3, 9, 6]
markerline, stemlines, baseline = plt.stem(x, y)
# Change marker color to red
# Which line below is correct?

hard

A. markerline.set_color('red')

B. markerline.get_markerfacecolor()[2].set_color('red')

C. markerline.get_markerfacecolor()[2] = 'red'

D. markerline.get_markerfacecolor()[2].set_facecolor('red')

Solution

1. Step 1: Understand plt.stem() return values

   It returns markerline, stemlines, baseline. markerline is a Line2D object representing all markers.

2. Step 2: Change marker color correctly

   Use markerline.set_color('red') to change the marker colors to red.

3. Final Answer:

   markerline.set_color('red') -> Option A

4. Quick Check:

   Use set_color() on markerline to change marker colors [OK]

Hint: Use set_color() on markerline to change marker colors [OK]

Common Mistakes:

• Trying to assign color directly to a list element
• Using get_markerfacecolor() incorrectly
• Confusing set_color() with set_facecolor()